Abstract
Schuler oscillation damping is one of the key technologies to improve the long-term precision of inertial navigation systems (INSs). Generally, a ship introduces the reference velocity to work on the external horizontal damping status to avoid the effects caused by maneuvers. However, the navigation accuracy is sensitive to the reference velocity error which will be affected by sea conditions and the ship’s maneuver. It is necessary to adjust the damping status dynamically as the change of the reference velocity error to ensure the accuracy and stability of INS. To address this problem, a novel variable damping system based on the variation of the reference velocity error is designed in this paper. First of all, this proposed method switched the damping status according to the variation of the reference velocity error in a certain period of time based on the principle of window detection. In addition, this paper designed a fuzzy controller to avoid the overshoot caused by the frequent switching of the damping status. What is more, a method of overshoot suppression was applied in this system. Simulation experiments were conducted to validate the theoretical analysis and the effectiveness of this method. Compared with the undamping system, constant damping system, and traditional variable damping system, the simulation results verified that the designed variable damping system can attenuate the system error caused by reference velocity error most effectively, thus improving the navigation accuracy of INS.
Highlights
inertial navigation systems (INSs) are widely employed in both military and civilian fields due to their numerous advantages
In view of this analysis, this paper proposed a novel method which switches the damping status according to the variation of reference velocity error and makes the damping coefficient ζ = 0:5 when the system is on damping status
The velocity information of the electromagnetic velocity log (EML) is compared with the outputs of a GPS to obtain the reference velocity error
Summary
INSs are widely employed in both military and civilian fields due to their numerous advantages. Compared with satellite navigation systems and radio navigation systems, INSs are completely autonomous navigation systems which have strong independence and good concealment and are invulnerable to external interference [1]. They use accelerometers and gyroscopes to get the acceleration and angular velocity to calculate the position, velocity, and attitude of carriers [2]. Because of the working principle of INS, the system has three kinds of periodic oscillation errors, i.e., the Schuler period, Earth period, and Foucault period error The amplitudes of these periodic oscillation errors are not attenuated and will continue to accumulate with time on account of the effects of gyroscope drift [3, 4]. To ensure the accuracy of INS, a damping correction network is added to turn INS into a stable system [5, 6]
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